The present invention relates to a system as defined in the preamble of claim 1.
In the prior art, a system for ECG monitoring as represented by the diagrams in FIGS. 1 and 2 is known. In FIG. 1, the same patient P is diagrammatically represented by two pictures of the torso, where the lower picture shows a standard four-point placement of measuring electrodes R, F, L and N (so-called limb electrodes). For the sake of clarity, the upper picture separately shows a standard placement of ECG measuring electrodes, i.e. precordial electrodes V1, V2, V3, V4, V5, V6 on the patient""s thorax. Together the limb electrodes and precordial electrodes form a so-called 12-lead connection system. A so-called 5-lead connection system also used in ECG measurement consists of limb electrodes together with one of the precordial electrodes, e.g. R, F, L, N and V1.
A 12-lead connection system as presented in FIGS. 1 and 2 comprises 1-10 signal leads, which are connected to corresponding measuring electrodes R, L, N, F; V1, V2, V3, V4, V5, V6 as mentioned above, attached to the patient P according to standard electrode placement Each signal lead 1-10 is provided with a first connector element 11. The system further comprises a collecting cable 12 with an adapter 24 at its end. The adapter 24 comprises a collecting connector 13 provided with second connector elements 14 for receiving the first connector elements 11 of the signal lead. At the other end of the cable 12 is a third connector element 15 The system further comprises an ECG apparatus 30, which comprises an amplifier unit 16.
The amplifier unit 16 is provided with a fourth connector element 17, to which the third connector element 15 of the collecting cable 12 is connected.
ECG monitoring and diagnostic so-called 12-lead ECG have traditionally been performed using different sets of equipment. Monitoring was performed as a continuous process using 3-lead or 5-lead equipment and 12-lead monitoring was generally performed when necessary under the supervision of a cardiologist as a short separate operation. However, it is possible to build an apparatus using modern electronics which brings the price of 12-lead ECG to a reasonable level, thus making it sensible to use continuous 12-lead monitoring. However, 12-lead equipment is more complicated than 5-lead equipment as it needs ten measuring electrodes as Mentioned above: R, F, L, N,; V1, V2, V3, V4, V5, V6 and therefore also ten patient cables, i.e. signal leads 1-10 from the amplifier to the patient""s skin. The end of the shielded collecting cable 12 in the prior-art 12-lead system is overloaded with a collecting connector 13, which is also presented in FIG. 2 as a diagram showing it in an end view. It comprises twenty connector elements 14 in all. Placed in the upper row on the right are circular connector elements 14 for the connector elements.11 of the signal leads 1-5 coming from the limb electrodes R, F, L, N, and one precordial electrode V1. Connected to the circular connector elements 141 in the left-hand part of the upper row are the connector elements 11 of the signal leads 6-10 coming from the precordial electrodes V2, V3, V4, V5 and V6. The shield of each signal lead 1-10 is connected to one of the rectangular connectors in the lower row (connections consistent with the AAMI standard), which are connected to a floating ground G.
Grounding of the shields of the signal leads has an importance especially in ECG monitoring performed during anesthesia, because surgical operations are often performed using a so-called diathermic device, i.e. an electric surgical knife, whose high-frequency electric current would otherwise confuse the ECG monitoring process.
The figure also shows protective resistors 23, whose function is to protect the amplifier electronics against the high-voltage pulse of a defibrillator. Two resistors are provided for each one of leads 1-5 because in most cases, in addition to ECG measurement, the patient""s respiration also needs to be monitored, which is done using a parallel apparatus measuring thorax impedance.
The problem with the prior-art system is that, in a 12-lead system, the collecting adapter is a very wide, large and heavy component when traditional, standardized shielded signal leads are used, in which each conductor runs inside a separate shield. The large size and weight are a problem in respect of usability, because the aforesaid collecting adapter is usually placed near the patient and can easily be dropped to the floor, where the adapter and the leads connected to it may be damaged.
The object of the invention is to eliminate the problems referred to above.
A specific object of the invention is to disclose a system which can work both as a 5-lead system and as a 12-lead system and in which it is possible to combine a 5-lead and a 12-lead amplifier connector and signal leads, allowing the same amplifier unit to function alternatively in a 5-lead system with shielded leads or in a 12-lead system with unshielded leads.
A further object of the invention is to disclose a system in which a small and light-weight collecting adapter can be used.
As for the features characteristic of the invention, reference is made to the claims presented below.
According to the invention the system comprises measuring attached to a patient in accordance with a standard electrode placement; signal leads connected to corresponding measuring electrodes each of said signal leads being provided with a first connector element; a collecting connector containing second connector elements for receiving the first connector elements; an ECG apparatus comprising an amplifier unit to which the measurement signals are passed from the collecting connector; and change-over switches which are so implemented that, in a first connection position, they will conduct the measurement signals from the measuring electrodes attached to the patient to the ECG apparatus so that the corresponding signal leads are electrically connected to the patient, while in a second connection position they establish a shielding ground connection for at least some of said signal leads.
Shielding is not necessarily needed in all monitoring situations, so it is possible to use signal leads substantially without a shielding ground connection.
In an embodiment of the system, the collecting connector is placed in the amplifier unit, and the signal leads are connected directly from the patient to the amplifier unit.
In an embodiment of the system, the system comprises a collecting cable between the signal leads and the amplifier unit. In this case, the collecting connector is connected to the collecting cable.
In an embodiment of the system, the collecting connector comprises a number of second connector elements corresponding to the number of measuring electrodes defined in the 12-lead ECG standard.
In an embodiment of the system, the changeover switches in their second connection position establish a shielding ground connection for a first group of signal leads via the connector elements in the collecting connector intended for a second group of signal leads
In an embodiment of the system, the measuring electrodes are connected to the patient in accordance with the 12-lead ECG standard. In this case, in order to accomplish a 12-lead ECG measurement, the changeover switches are in the said first position to pass the measurement signals from all measuring electrodes to signal processing in the ECG apparatus the signal leads now being electrically connected to the patient.
In an embodiment of the system, the measuring electrodes are connected to the patient in accordance with the 5-lead ECG standard. In this case, to accomplish a 5-lead ECG measurement with grounded shielding, the change-over switches are in the said second position, the first group of signal leads now having a shielding ground connection to a floating ground.
In an embodiment of the system, the second connector elements in the collecting connector are arranged in two adjacent rows, where the second connector elements in one row are disposed in paired alignment with the connector elements in the other row.
In an embodiment of the system, the changeover switches are disposed in the amplifier unit.
In an embodiment of the system, the changeover switches are controllable analog switches.
In an embodiment of the system, the system comprises a control device for the control of the change-over switches.
In an embodiment of the system, the control device comprises means allowing the change-over switches to be controlled by the user.
In an embodiment of the system, the control device comprises detection means so implemented that they will automatically detect the connection state (lead on/lead off) of a measuring electrode to a patient; and means for selecting the connection position of the change-over switches from between said first connection position and said second connection position on the basis of said automatic detection.
In an embodiment of the system, the detection means are so implemented that they will automatically detect convection of the measuring electrodes to a patient by measuring the resistance of the measuring electrodes.
In an embodiment of the system, the signal leads comprise a set of standard precordial leads and a set of standard limb leads.
In an embodiment of the system, the connection elements for the limb leads and for one precordial lead are arranged in the first row in the collecting connector, and the connection elements for the rest of the precordial leads are arranged in the second row in the collecting connector the second row being in paired alignment with said first row.
In an embodiment of the system one of the limb leads is defined to be unshielded in both 5-lead and 12-lead measurement mode. The detection means are disposed to continuously monitor the connection state (lead on/lead off) of one precordial lead to determine which of the monitoring modes (5-lead or 12-lead) to be used.
In an embodiment of the system said lead being unshielded and continuously monitored is the precordial lead for which a connecting element is dedicated in the second row of connecting elements at the collecting connector, said connecting element in the second row being in paired alignment with another connecting element in the first row of connecting elements at the collecting connector, said another connecting element in the first row being dedicated f or the Neutral lead from the set of standard limb leads.
In an embodiment of the system, the detection means are so implemented that they will automatically identify the signal lead types used, by measuring the capacitances regardless of whether the leads are connected to a patient or not.
In an embodiment of the system the collecting connector comprises a separate shield connector common for all signal leads.
In an embodiment of the system the collecting connector for a 12-lead cable is mechanically coded, so as not to mare with a standard 5-lead connector.